An ac motor Induction engine or asynchronous motor can be an AC electric electric motor in which the electric energy in the rotor had a need to create torque is obtained by electromagnetic induction from the magnetic field of the stator winding. … An induction motor’s rotor could be either wound type or squirrel-cage type.
Benefits of AC Induction Motors are:
Induction motors are simple and rugged in structure. They are better quality and can operate in virtually any environmental condition
Induction motors are cheaper in cost due to simple rotor construction, absence of brushes, commutators, and slip rings
They are maintenance free motors unlike dc motors due to the lack of brushes, commutators and slip rings
Induction motors can be operated in polluted and explosive conditions as they don’t have brushes that may cause sparks
AC Induction motors are Asynchronous Machines meaning that the rotor does not turn at the specific same speed since the stator’s rotating magnetic field. Some difference in the rotor and 
stator quickness is necessary to be able to create the induction into the rotor. The difference between your two is called the slip. Slip must be kept in a optimal range to ensure that the motor to operate efficiently. Roboteq AC Induction controllers can be configured to operate in another of three modes:
Scallar (or Volts per Hertz): an Open loop mode in which a order causes a simultaneous, fixed-ratio Frequency and Voltage modify.
Controlled Slip: a Closed Loop speed where voltage and frequency are controlled in order to keep slip within a narrow range while operating at a desired speed.
Field Oriented Control (Vector Drive): a Closed Loop Rate and Torque control that works by optimizing the rotating field of the stator vs. this of the induced field in the rotor.
Discover this video from Learning Engineering for a visual illustration about how AC Induction Motors are constructed and function.